1. Field of the Invention
The present invention relates to transient web material storage devices and more particularly such devices having the ability to simultaneously receive and deliver web material such as film. The device is particularly suited to those situations where there is a significant difference between the rate at which material is supplied and withdrawn.
2. Description of the Prior Art
It is known in the prior art to use a slack box for a transient film storage device. See for example commonly assigned U.S. Pat. No. 3,693,859, issued Sept. 26, 1972. The slack box stores film material at the feed and/or supply end of a continuously operating machine such as a photographic film processing machine. Use of the slack box permits intermittent stopping of the film transport for short periods of time without affecting the continuous operation of the processing device. A problem is encountered with the use of slack boxes when there is a significant difference between the rate at which film is fed into the boxes and the rate at which film is withdrawn from the boxes. When this is the case, the slack box must be relatively large to permit continuous operation of the processing machine.
Arrangements for exposing and processing film are well known. For instance, one system known to the prior art utilizes a separate camera and a separate processor to expose and process web material in the form of microfilm. The camera has a supply housing in which a roll of unexposed microfilm is positioned, an exposure station at which the microfilm is exposed, and a take-up housing in which the microfilm is stored after exposure. When it is desired to process the exposed microfilm, for instance at the end of a roll of microfilm, the take-up housing is opened and the roll of exposed microfilm is removed therefrom and transferred to a processing apparatus. The transfer operation either occurs under controlled light conditions or the exposed film is stored in a separate light-tight container. In either case, the operation of the camera is delayed for a period of time while the transfer occurs. Obviously, the film cannot be fed directly from the microfilm camera to the processing device because the rate at which film is exposed is substantially slower than the rate at which it is fed through the processing apparatus. In some situations, the filming of documents on microfilm is randomly intermittent, with intervals of hours or days between filming sessions. The delay that occurs between the time the film is loaded and processing of the roll begins often makes the earlier filmed documents inaccessible for an undesirably long period of time.
The resolution of this problem requires either the retention of the original documents, which militates against the purpose of microfilming, or requires the processing of partially exposed rolls of film, resulting in the possibility that the unexposed microfilm within the camera may be inadvertently exposed during transfer.